ICSV22, Florence (Italy) 12-16 July 2015 1 SOUND ABSORPTION PROPERTIES OF REED Francesco Asdrubali, Francesco D’Alessandro, Samuele Schiavoni and Nicholas Mencarelli CIRIAF, University of Perugia, via G. Duranti 67, 06123 Perugia, Italy e-mail: francesco.asdrubali@unipg.it The use of reed (Phragmites australis) as building material is common in many countries all over the world. This material was especially employed in lowlands regions, thanks to its abundance and good performance related to thermal and hygrometric comfort. Today the use of reed is not widespread and limited to some applications in green architecture, especially as thermal/sound insulating materials in roofs and walls, both as internal or external insula- tion covered with plaster. The scope of the present paper is to study the sound absorption properties of reeds using an impedance tube according to ISO 10534-2. Several samples were tested in order to study the influence of the manufacturing process, for instance the thickness and the spatial configuration (reeds parallel or perpendicular to the sound wave). The results show that, if properly designed, reed panels can represent a sustainable and low cost alternative to common absorbers. 1. Introduction Several studies were performed in recent years to characterize natural and sustainable materials for acoustic applications [1]. The low cost and the great diffusion and availability of reeds encour- aged researches in this field. In the building sector, thermal insulation panels made of reed are cur- rently commercialized, particularly in Eastern Europe. Reed panels are usually characterized by good values of thermal conductivity: a value of thermal conductivity around 0.055 W/m 2 for reed panels with density between 130 and 190 kg/m 3 has been measured in the Thermotechnical Labora- tory of the University of Perugia [2]. The acoustical properties of reeds were first evaluated within the activities of the Holiwood pro- ject [3]. The sound absorption coefficient of three configurations of reed was measured using an impedance tube, one parallel and two perpendicular (in one case reeds were placed with a crossed configuration) to the incident wave. The measured values were then compared with modelled data, but a poor correlation was obtained. Nevertheless the samples showed interesting values of the sound absorption coefficients, even if the analysis was limited to low-medium frequencies (100- 1000 Hz). A deeper analysis was performed by Oldham et al. [4], which extended the analysis to higher frequencies in the impedance tube and performed sound absorption tests in a reverberation room. Samples tested in the impedance tube were realized placing the reeds parallel to the incident wave. The results of measurements performed on samples with thickness greater than 85 mm showed val-